Different from a conventional analog content, a digital content of music and so forth can be copied by a plural number of times without any deterioration of the quality. Therefore, in recent years, together with popularization of the Internet and increase in speed and capacity of a PC (personal computer) and so forth, illegal distribution, exchange and so forth of a content without any approval of its author is increasing.
In order to prevent such illegal acts, a copyright management system which makes use of a DRM (Digital Rights Management; digital copyright management) which applies restrictions to circulation and utilization of a content is being popularized. In such a copyright management system as just mentioned, a method (hereinafter referred to as “check-in check-out system”) which restricts utilization (reproduction, copying and so forth) of a content based on utilization conditions described in a license (right information) as proposed by the SDMI (Secure Digital Music Initiative) and so forth to manage the copyright of the content is popularly used (refer to, for example, Patent Document 1).    Patent Document 1: Japanese Patent Laid-Open No. 2003-296486